Process of producing magnesium and calcium carbonates.



PATENTED JULY 21, 1903..

- F. s. YOUNG. PROCESS OF PRODUGING MAGNESIUM AND CALCIUM GARBONATES.

APPLIUATION FILED APR. 3, 1902.

2 SHEETS-SHEET 1 N0 MODEL.

WITNESSES:

No. 734,030. I PATENTED JULY 21, 1903.

' F. S. YOUNG.

PROCESS 0F PRODUCING MAGNESIUM AND GALGIUM OARBONATES.

APPLIOAT ION FILED APR. 3. 1902.

N0 MODEL. 2 SHEETS-SHEET 2.

WITNESSES: INV NTORfl gcwww/fifi UNITED STATES Patented July 21,

I PATENT OFFICE.

PROCESS OF PRODUCING MAGNESIUM AND CALCIUM CARBONATES.

SPECIFICATION forming part of Letters Patent No. 734,030, dated July 21, 1903.

' Application filed April 3, 1902. 7 Serial No. 101,177. (No specimens.)

To all whom it may concern:

Be it known that I, FRANK S. YOUNG, a citizen of the United States, residing at Norristown, in the county of Montgomery and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Producing Magnesium and Calcium Carbonates from Dolomite, of which the following is. a specification, reference being had to the ac-- the calcium from the magnesium salts. The

objections to this process are the entire loss of lime, the comparative incompleteness of the separation effected, and the large quantity of water necessarily present in the carbonate solution, which must be heated in order to precipitate the carbonate. By my p'rocess I effect the separation of the two bases by settling or precipitation during thatstage of the process when both of the oxide obtained from the calcined dolomite are mixed with.

water and prior to the carbonation. In this a more complete separation, and obtain a stronger bicarbonate solution, requiring less heat to effect the recoveryof the carbonate. Furthermore, the small quantity of lime present when the magnesia is carbonated enables me to employ better methods of carbonation than can otherwise be used.

In the accompanying drawings, Figure l is a plan illustrating in diagrammatic form an apparatus suitable for carrying out my process. Fig. 2 is an elevation of the same. Fig. 3 is a plan view of the magnesia-carbonating tower. Fig. 4 is'a sectional elevation of the same.

As the first step of my process dolomite is calcined in the kiln A, which does not differ from those heretofore used for this purpose. Dolomite is a mixture of carbonates of calcium and magnesium, and as a result of the continuously drawn ofi by pipe e.

calcining process the carbonic acid is driven oif, leaving a friable mass consisting of lime and magnesia, with some impurities, chiefly silica, alumina, and'iron. The carbonic-acid gas driven off at the top of the kiln is collected and carried by a downcomer a to a gascompressor a by which the gas is compressed and driven continuously into the carbonicacid-gas-supply pipe at. The calcined dolomite is taken 0E from the bottom of the kiln and delivered by a hoist 1) into one of a series of slaking-tanks B, Where it is mixed with a sufficient amount of water from the water-supplypipez to properly slake the lime. From the tanks the slaked mixture is led into a reservoir C, from whence it is pumped by pump c into the solution-tank D, where it is mixed with cold water from the Water-supply pipe 2. In both the reservoir 0 and the solution-tank D the contents are kept agitated either by mechanical devices or by a current of air blown through. In the solution-tank D the amount of cold water added is suliicient to take up in solution the greater part of the calcium hydrate, the magnesia and other insoluble contents being kept in suspension by agitation. From tank D the contents are pumped by pump (1 into the large settlingtower E. This tower is furnished with a series of downwardly-sloping shelves perforated centrally, and as the milky liquid passes into the tower the magnesia and other insoluble matter slide down gradually to the bottom into a mud-drum, while a clear solution of calcium hydroxid appears at the top and is It will therefore be observed that the separation of the bases is effected, while both the lime and magnesia are in the form of oxids, (using that term as I do in a sufficiently broad sense to include hydroxide.) The lime-Water from the top is led by pipe 6 into a lime-carbonating tower F, where it is subjected to a current of carbonic-acid gas drivenin at the bottom from the supply-pipe a. This converts the lime into an insoluble carbonate, which is recovered either by precipitation or by filtration, for which latter purpose the filter G is provided.

From the mud-drum at the bottom of the settling tower E the magnesia sludge is pumped by a pump 9 into a small tank H, where the proper amount of water from supply-pipe z is mingled with it, the mixture being agitated either mechanically or by an airblast. From this tank the water, with the magnesia and other salts in suspension, is pumped by a pump 7t into the magnesia-carbonating tower J. This tower is furnished with a series of gratings S S, on each of which is placed a layer of broken marble or dolomite. As the water carrying magnesia trickles down through the stone on these gratings it is subjected to the action of carbonic-acid gas delivered at the bottom of the tower from pipe at, by means of which the milk of magnesia is converted into a solution of magnesium bicarbonate, while any lime which is still present in the solution is by the same operation converted into insoluble calcium carbonate. As the lime forms only a small part of the matter present in the milk which entered the tower, the resulting solution of magnesium bicarbonate is stronger than can be obtained where all of the lime of the dolomite is still present. The contents of this tank are then pumped by pumpj into a filter-press K, whereby all of the insoluble impurities (e. g., lime, alumina, silica, or iron) are removed, and a clear solution of magnesium bicarbonate is thence pumped by pump 1 into a heat-interchanger L, wherein by a coil or otherwise the solution is partially heated by the waste liquid from the next compartment. From the heatinterchanger the heated bicarbonate solution is run into a boiling-tank M, where its temperature is raised to the boiling-point by steam blown in at the bottom. This boiling process decomposes the magnesium bicarbonate into an insoluble carbonate of magnesium, setting free carbon dioxid which is evolved. The precipitated magnesium carbonate is removed from its water of suspension by filtration in the filter Q, the waste liquid being run through the heat-interchanger, as previously explained. From the filter the pure magnesium carbonate is removed and dried.

As a result of my process both the magnesium and calcium carbonate are obtained in a condition of great purity. I may further facilitate the recovery of the magnesium carbonate from the bicarbonate solution by adding calcined magnesite, as described in United States Letters Patent No. 689,345, granted to me under date of December 17, 1901; but instead of this I prefer to employ a portion of the magnesia sludge from the bottom of the carbonating-tank J. This magnesia sludge when introduced into the bicarbonate solution reduces the magnesia salt to a carbonate in the man ner described in the patent to which I have referred, and it is one of the advantages of my present process that I am able by reason of the preliminary separation of the lime and magnesia to obtain the requisite magnesium oxid for effecting this reaction as a part of the process itself instead of from an external source.

Having thus described my invention, I claim- 1. The process of obtaining magnesium carbonate from dolomite, which consists; first, in allowing a mixture of water and calcined dolomite to settle until the magnesia has been precipitated; second, in withdrawing the precipitated magnesia and subjecting it to carbonation, whereby a solution of magnesium bicarbonate is produced; third, in reducing the magnesium bicarbonate to carbonate and recovering the same, substantially as described.

2. The process of obtaining magnesium and calcium carbonates from dolomite, which consists; first, in allowing a mixture of water and calcined dolomite to settle until the lime goes into solution and the magnesiais precipitated; second, in subjecting the lime-water thus produced to carbonation, whereby the lime is recovered, and also subjecting the magnesia mixed with water to carbonation, whereby a solution of magnesium bicarbonate is produced; and third, in reducing the magnesium bicarbonate to carbonate and recovering the same, substantially as described.

3. The process of obtaining magnesium carbonate from dolomite which consists in, first, allowing a mixture of water and calcined dolomite to settle until the lime goes into solution and the magnesia is precipitated; second, subjecting part of the magnesia thus obtained to carbonation, whereby a solution of magnesium bicarbonate is produced; third, adding to the bicarbonate solution the rest of the magnesia, and recovering the resulting carbonate, substantially as described.

4. The process of obtaining magnesium and calcium carbonates from dolomite, which consists in allowing a mixture of water and calcined dolomite to settle until the lime goes into solution and the magnesiais precipitated; subjecting the lime to carbonation and recovering the carbonate; subjecting the magnesia to carbonation, whereby a solution of magnesium bicarbonate is produced; and reducing the magnesium bicarbonate to carbonate, and recovering the same, substantially as described.

5. The process of obtaining magnesium carbonate which consists in allowing a milk or emulsion of magnesia to drip down through an atmosphere of carbonic-acid gas in a percolating-tower; whereby a solution of magnesium bicarbonate is produced; and then reducing the bicarbonate in the solution to carbonate by the addition of magnesia and recoyering the same, substantially as described.

FRANK S. YOUNG.

Witnesses:

JAMES H. BELL, E. REESE. 

